Steel for mechanical structures, method of hot forming of steel element and steel element manufactured in this way

摘要

The invention relates to a steel for mechanical construction, characterized in that its composition is, in percentages by weight: 0,35 ≦ c ≦ 2,5%; 0,10% ≦ mn ≦ 2,5%; 0,60% ≦ si ≦ 3,0%; traces ≦ cr ≦ 4,5%; traces ≦ mo ≦ 2,0%; traces ≦ ni ≦ 4,5%; traces ≦ v ≦ 0,5%; traces ≦ cu ≦ 4% with cu ≦ ni% + 0,6 if%, if cu ≧ 0,5%; traces ≦ al ≦ 0,060%; traces ≦ ca ≤ 0,050%; traces ≦ b ≦ 0,01%; traces ≦ s ≦ 0,200%; traces ≦ t e ≦ 0,020%; traces ≤ is ≦ 0,040%; traces ≦ pb ≦ 0,070%; traces ≦ nb ≦ 0,050%; traces ≦ ti ≦ 0,050%; the remainder being iron and impurities resulting from the élaboration.l' invention also relates to a method of putting in the form of a piece of steel, characterized in that it provides a steel billet of the above composition, the billet is heated at a temperature between the solidus and liquidus in order to obtain a liquid phase and a solid phase globular, a shaping by thixoforging of said bar in order to obtain said piece, and a cooling of said piece. Finally, the invention relates to a steel part thus obtained.